Abstract
Glycoalkaloids are toxic compounds that are synthesized by many Solanum species. Glycoalkaloid biosynthesis is influenced by plant genetic and environmental conditions. Although many studies have shown that light is an important factor affecting glycoalkaloid biosynthesis, the specific mechanism is currently unknown. Chlorophyll and carotenoid biosynthesis depend on light signal transduction and share some intermediate metabolites with the glycoalkaloid biosynthetic pathway. Here, we used virus-induced gene silencing to silence genes encoding phytoene desaturase (PDS) and magnesium chelatase (CHLI and CHLH) to reduce chlorophyll and carotenoid levels in eggplant leaves. Quantification of carotenoid and chlorophyll levels is analyzed by LC/PDA/APCI/MS and semipolar metabolite profiling by LC/HESI/MS. Notably, the resulting lines showed decreases in glycoalkaloid production. We further found that the expression of some genes involved in the production of glycoalkaloids and other metabolites were suppressed in these silenced lines. Our results indicate that photosynthetic pigment accumulation affects steroidal glycoalkaloid biosynthesis in eggplant leaves. This finding lays the foundation for reducing the levels of endogenous antinutritional compounds in crops.
Highlights
Steroidal glycoalkaloids (SGAs) are a class of nitrogenous secondary metabolites that are synthesized in many organs of Solanaceous plants including tomato (Solanum lycopersicum), potato (Solanum tuberosum) and eggplant (Solanum melongena) [1, 2]
SGAs act as phytoanticipins, providing the plant with a preexisting defence against a broad range of pathogens, when agro-infiltration, SGA as a protector against Agrobacterium invasion, so the SGA biosynthesis-related gene expression and SGA content increased (Figs 3 and 4)
Considering a large number of regulated steps and the differential regulation observed as mentioned, I cannot exclude the possibilities of the involvement of additional mechanisms, such as indirect regulation through other transcription factors or metabolite-mediated feedback regulation, which would explain why ChlI and ChlH-silencing activated the expression of some GAME genes, such as GAME6,GAME12 (Fig 4)
Summary
Steroidal glycoalkaloids (SGAs) are a class of nitrogenous secondary metabolites that are synthesized in many organs of Solanaceous plants including tomato (Solanum lycopersicum), potato (Solanum tuberosum) and eggplant (Solanum melongena) [1, 2]. SGAs inhibit the activity of acetylcholine enzymes and have a negative effect on the nervous and digestive systems of vertebrate animals [1]. As well as removal of antinutritional traits, are needed. Eggplant is an agronomically important vegetable, and is cultivated and consumed in many countries, which play an important role in the human diet. The research on the biosynthesis of antinutrition glycoalkaloid is essential in eggplant. There have been many studies on the biosynthesis of glycoalkaloids in tomatoes and potatoes, due to their low contents and complicated
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